Why is my iPhone slowing down, and how do I fix it?

Why is my iPhone slowing down, and how do I fix it?

Probably too many things left opened after using them. It's basically like a computer having too many things running in the background.

To fix your iPhone's speed:
First go to the Home Screen.
Next double tap your home button. You should now see a popup of another row setup. The apps on that row are what is running in the background.
To end it, simply hold the icon as you would to delete it. Don't worry, nothing will be deleted.
Keep ending each app until nothing is left in the row.